Galileo Galilei

Padua and Astronomy

The Starry Messenger

Rome celebrated the coming of the new century with a great
jubilee: a million pilgrims converged on the city, and the ailing
pope, Clement VIII, heard the confessions of heretics and blessed
the progress of the Counter-Reformation from the balcony of his
palace. Meanwhile, Galileo was facing new family problems; since
his father's death early in the previous decade, he had become
the head of the family, and its principle breadwinner. In this
capacity, he supported his brother Michelangelo's fumbling attempts
to become a professional musician, which eventually landed him
a post in the Polish court, but not before bleeding considerable
sums of money from Galileo's purse. In 1604, the Polish appointment
came to an end, and again Galileo was forced to support his brother
until another job came along, this time in the German principality
of Bavaria. Meanwhile, Galileo's sister Livia, formerly a nun,
had left her religious order in the hopes of attracting a husband,
and when she found one, it was Galileo who had to pay her dowry.
Moreover, in the first decade of the 17th century Galileo's mistress
Marina gave birth to three children; Galileo was carrying a heavy
financial burden on his professor's salary.

Meanwhile, in 1604, a new star had appeared in the sky,
posing a remarkable challenge to the Ptolemaic system, which followed Aristotle
in holding that the heavens were fixed and eternal. The star became
known as Kepler's Nova, after the iconoclastic German astronomer,
who became famously associated with the star by arguing that it
shone from a high and distant location, rather than from a place
close to the moon, as more conservative scholars argued. In a
famous series of lectures in 1604 and 1605, Galileo took Kepler's side
in the debate, ruffling the feathers of his traditionalist rivals
at the university. But more mundane concerns soon tugged at him: during
his annual summer visit to Florence, his mounting debts caught
up with him, and his creditors threatened to take him to court.
The financial pressure abated only when Galileo agreed to tutor
Prince Cosimo, son of Tuscany's Grand Duchess, and grandson of the
first Cosimo de Medici, who had ruled Tuscany at Galileo's birth.
With this new pupil, and the consequent support of the Grand Duchess,
Galileo was able to obtain a necessary salary increase, and rescue
his sinking financial fortunes.

But by the end of the decade, Galileo was growing dissatisfied with
Padua. He felt under-appreciated and overworked: he earned only
half the salary of the typical Aristotelian professor, and he taught
a growing collection of pupils. These pupils hailed from noble
European families, and Galileo had to meet their needs not only
out of his obligations as a teacher, but out of political obligations;
to refuse to attend to these students' needs would be to lose the
backing of powerful families. But his teaching duties took time away
from his private studies, and crucial questions were goading Galileo.

He began to yearn for a new appointment, ideally in his
native Florence, and he continued to curry favor with the royal
family of Tuscany in the hopes of obtaining their patronage. But
then, in the summer of 1609, news arrived in Italy of the invention
of the telescope, by a Dutch spectacle-maker named Hans Lippershey.
Intrigued, Galileo began assembling his own device, at first thinking only
of its value in a military campaign and the profits to be made from
selling it to the Venetian state. But hearing that the Dutchman himself
was coming to Venice, he threw himself into experiments with lenses,
and by late August he had produced his own telescope, which was
presented as a gift to the Venetian State. The grateful Senate
voted to double his salary. In the autumn months that followed,
Galileo continued to tinker with his lenses, and eventually increased
the magnification of the telescope four hundred times. Then, fatefully,
he turned the device toward the sky and began making observations.
The world of science would never be the same.

Galileo's telescope opened a window on the heavens that
previous astronomers could have only wished for: suddenly the moon, the
backdrop of stars, and the planets were revealed as having properties
never before imagined. The moon, a regular and polished disc to
the naked eye, was revealed to have a mountainous surface, covered
with craters, basins, and peaks, much like the earth itself. This notion
came as a shock, both to conventional science and to the Church;
how could supposedly perfect heavenly bodies resemble the earth?
Meanwhile, thousands of new stars suddenly sprang into visibility,
filling out constellations and rendering the galaxy a glittering
carpet of lights. And then, in January 1610, Galileo's telescope
revealed four of the nine moons of Jupiter; these moons "move...
around another very great star [Venus]," he wrote, in the same
way as Mercury and Venus, and peradventure the other known planets,
move around the sun."

Here, at last, was concrete evidence for Copernicus's
system, which had long been confined to the realm of mathematical
models. If Jupiter had attendant moons, just as Earth did, then
it was reasonable to assume that Jupiter and Earth were similar
bodies–planets orbited by satellites, and orbiting, themselves,
around a larger sun.